Method for hydroforming naphthas



June 14, 1955 J. WEIKART 2,710,826

METHOD FOR HYDROFORMING NAPHTHAS Filed Nov. 1, 1949 MAPHTHA FEED STOCK.

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NORMALLY GAsEous IZODUCT -p FQAQT I ONATION E lM Phov an NAPHT HA T QoDucT John. JEL'Kar t 'jnvenbor bsfi ryzgw qbbo nag v METHOD F OR HYDROFORMING NAPHTHAS John Weikart, Elizabeth, N. J., assignor to Esso Research and Engineering Company, a corporation of Delaware Application November 1, 1949, Serial No. 124,748

3 Claims. (Cl. 196-49) This invention relates to a process for the treatment of hydrocarbon fractions boiling within the motor fuel range in order to increase or improve their knock rating. More particularly, the present invention pertains to the hydroforming of hydrocarbon fractions boiling within the motor fuel range in two reaction stages in order to produce high yields of high anti-knock constituents.

Increases in the compression ratio of internal combustion engines have placed greater demands upon gasoline type motor fuels for efficient, knock-free operation in such engines. by providing improved base stocks and by the use of additives such as tetraethyl lead. Hydroforming is one of the most promising methods for upgrading naphthas to provide improved base stocks because of its superior yield-octane number relationship and because hydroformed gasolines give less engine deposits than thermally reformed naphthas.

Catalytic reforming or hydroforming of naphtha fractions is ordinarly conducted at temperatures between 750 and 1150" F. and at pressures of from about atmospheric to about 1000 lbs. per sq. inch and in the presence of catalysts generally comprising oxides or sulfides of metals or groups 1V, V, VI, Vll and VIII of the periodic system alone or on supports or spacing agents. Preferred catalysts for this process have been molybdenum oxide, chromium oxide and tungsten oxide preferably on activated alumina or on zinc aluminate spinel.

It has been proposed in U. S. Patent 2,285,727 to treat gasolines of inferior knock rating in two stages, first with a metal effective in dehydrogenating naphthenes and then with a catalyst containing a metal oxide effective in dehydrogenating and cyclicizing parafiins. It has also been proposed in U. S. Patent 2,409,695 to upgrade a petroleum naphtha in two stages, first by contact with a molybdenum oxide-alumina catalyst at temperatures within the range of 850 to 1100 F. in the presence of hydrogen-containing gas and at pressures of at least 100 lbs. per sq. in. and then subjecting the reaction products from this treatment, preferably after removal of aromatics, to a further treatment in a second reaction zone in contact with a I promoted chromia-alumina catalyst at temperatures within the range of 850 to 1050 F. and at pressures substantially lower than was used in the first stage. However, there is still a demand for improved catalysts and techniques for upgrading naphthas.

It is the object of this invention to provide the art with an improved method of upgrading hydrocarbon fractions boiling within the naphtha or motor fuel range.

It is a further object of this invention to provide the art with a method whereby naphtha fractions may be upgraded by a hydroforming treatment with high yields and octane number relationships.

These and other objects will appear more clearly from the detailed specification and claims which follow.

It has now been found that hydrocarbon fractions boiling within the motor fuel or naphtha range can be upgraded with high yield-octane number relationship by These demands, in general, have been met nited States Patent treatment with a molybdena-containing catalyst in two stages, the first at high pressures of about 200 to 1000 lbs. per sq. inch and at temperatures of about 850 to 950 F. and the second at pressures of atmospheric to 60 lbs. per sq. inch and at temperatures of about 925 to 1000" F. The higher the pressure in the first stage, the lower the amount of carbon formed therein. At pressures of about 750 to 1000 lbs. per sq. in. the amount of carbon formed in the reforming ordinary naphtha fractions is so small that the reaction zone can be operated continuously, i.- e., without regeneration and only a sufiicient number of secondary or low pressure reaction zones need be provided to permit continuous operation. Usually two secondary reactors would suffice to permit continuous operation, one being on stream while the other.

is subjected to purging and regeneration.

If the first reaction stage is operated at about 200-300 lbs. per sq. in. and the second reaction stage is operated at about 50 lbs. per sq. in. the amount of carbon formed in the first stage is about one fourth that formed in the second stage. In view of the extreme unbalance in carbon yields between the two stages, 20 and 80% of total carbon in the high and low pressure stages respectively it would not be feasible to regenerate both stages at the same interval, employing the same regeneration equipment. This difficulty can be overcome by feeding a naphtha/ kerosene cut to the high pressure stage and flash separating the naphtha and kerosene between the two stages and feeding only the naphtha portion to the second stage. in this way, carbon yield in the two stages can be substantially equalized, permitting regeneration of both stages at the same interval and with the same regeneration system with no increase in investment.

The molybdena-containing catalysts used in accordance with the invention are prepared, for example, by impregnating activated alumina or a zinc aluminate spinel base with ammonium molybdate solution, drying and activating the resultant compositions. Catalysts prepared by coprecipitation of M003 and A1203 are not satisfactory for the present process. The catalysts should contain from about 5 to 25 wt. per cent, preferably to 12 wt. per cent of M003, the remainder being essen-.

tially activated alumina or zinc aluminate spinel.

The present process is particularly effective for upgrading naphtha fractions which contain relatively low amounts of naphthenic constituents and which conversely contain large amounts of paraffinic constituents. This process is preferably applied to naphthas containing less than to of naphthenic constituents.

Reference is made to the accompanying drawing illustrating a flow diagram of the process in accordance with the present invention. A naphtha feed stock is supplied to the system through inlet line 1. The feed stock is discharged into the first reaction stage 2 which is charged with a suitable molybdena-containing catalyst, for example, one comprising about 10 wt. percent M003 on activated alumina or on zinc aluminate spinel. The first reaction stage is maintained at temperatures between 850 and 950 F. and at pressures between 200 and 300 lbs. per sq. inch. The naphtha feed is retained in the first reaction stage for a period suflicient to effect conversion of all or substantially all of the naphthenic constituents in the feed stock into aromatics, but sufiiciently short to leave the parafiins substantially unchanged.

The reaction products from the first reaction stage 2 are conducted through line 3 into the second reaction stage 4. If desired, the reaction products from the first reaction stage may be subjected to fractionation prior to subjecting the same to the second reaction stage. In this case, the reaction products from the first reaction stage would be supplied to the fractionation means 5 by means of the line 12. Normally gaseous materials are withdrawn from the fractionation means 5 through line 6 while the liquid products are discharged through line 7 and supplied to the second reaction stage 4.

In the second reaction stage 4, the pretreated naphtha is treated by contact with a molybdena-containing catalyst, for example one containing about wt. percent M003 on activated alumina or on zinc aluminate spinel. The second reaction stage is maintained at temperatures between 925 and 1000 F. and at pressures between atmospheric and 60 lbs. per sq. inch. The pretreated naphtha is retained in the second reaction stage until a substantial portion of the paratfinic constituents in the feed is aromatized. The reaction products from the second reaction stage 4 are discharged through line 8 into fractionation means 9. Normally gaseous products are discharged from the fractionation means 9 at 10 while the improved naphtha product is discharged through line 11.

Contact of the feed stock with the molybdena-containing catalyst in either or in both of the reaction stages may be effected in either a fixed bed or in a moving or fluidized bed. Auxiliary heating means may be arranged on or in each of the reaction stages for supplying heat thereto in order that the reaction may be conducted isotherm ally and/or, if desired, with an inverse temperature gradient, i. e., higher outlet than inlet temperature.

Hydrogen-containing diluent gas is added to both of the reaction stages in order to reduce the formation of coke. The hydrogen/ hydrocarbon mol ratio is ordinarily lower than 10/1 and is preferably in the range of from 1/1 to 4/1. Recycle or process gas containing from 70 to 90% hydrogen and the remainder being light, gaseous hydrocarbons may be used as the diluent gas.

In order to balance carbon formation in the two pressure stages, a naphtha/kerosene cut is charged in admixture with hydrogen-containing gas to a reactor (.9) filled with a molybdena-containiug hydroforming catalyst operating at 200 pounds or higher pressure and 800 to 950 F. average catalyst temperature in order to dehydrogenate the feed stock naphthenes to aromatics. The effluents from the reactor are expanded through a turbine, or other energy recovery device to lower pressures and passed through a heat exchanger for temperature control to a flash tower wherein the hydrogen-containing recycle gas and naphtha boiling up to 300 or 400' F. are separated overhead and the heavy naphtha/ kerosene above 300 to 400 F. is taken as bottoms from the flash tower. The overhead gaseous stream from the flash tower is then passed to a reactor (s) filled with a molybdena-containing hydroforming or aromatization catalyst operating at 50 pounds, or lower pressure, and average catalyst temperatures in the range of 925 to 1000 F., depending on the desired overall severity of this process, in order to aromatize the paratfins in the naphtha portion of the feed stock. The eflluents from this low pressure operation are cooled to essentially room temperature and passed to a flash tower wherein a hydrogencontaining gas is separated overhead, all or a portion of this gas being returned to mix with naphtha/kerosene feed stock at the process inlet or at the entrance to the first reactor. The bottoms from this flash tower following the low pressure catalytic treatment are unfinished high octane gasoline. The bottoms from the other flash tower, located between the high and low pressure catalytic treatment steps, consists of a mixture of aromatics, parafi'rns and essentially no naphthenes, the naphthenes having been converted to aromatics, which can be separated by well known extraction methods, such as S02 treating to yield an aromatic concentrate and a paratfin concentrate. The former would appear saleable directly as premium solvent or, after suitable fractionation, for aromatic petro-chemical raw materials. The paraflin fraction would appear to be a high quality diesel fuel, perhaps being to the diesel fuel pool what alkylate and polymer gasoline are to the refinery gasoline pool, or perhaps saleable as a petro-chemical raw material.

The following example is illustrative of the present invention:

EXAMPLE A 200/300 PVT naphtha was first hydroformed over a catalyst comprising 10 wt. percent M003 and 90% of activated alumina. The feed stock was first passed through the reaction zone at 250 lbs. per sq. in. and low temperature, 894 F. at mild severity, 93.5% C4+hydroformate yield. The total yield product (without rerunning containing /3 of C4 and ofCs produced) was then processed over the same catalyst at lbs. per sq. in. and at sufficiently high average catalyst temperature to reach a practical octane level, actually 93.3 research octane on (Is/430 FVT hydroformate. The data from these runs is summarized in Table I below:

Table I .---Tw0 pressure hydmfnrmfng BJD. adiabatic hydrotorming-d'resh 10% M003 on activated alumina catalyst. Kuwait 200/300 FVI naphtha.]

Two Pressure 1 Operation 1st 2nd E Over- Pass Pass all Pressure, P. s. i. g 250 50 Research Octane N c. on 05/430 FVT 93. 3 Operating Conditions:

Temperatures, F.

Inlet 960 1, 020 k 060 Lead Reactor, Avg. 907 943 t 894 Tall Reactor, Avg 876 944 943 Overall, Avg... 894 943 910 Feed Rate, v/hr./v. 0.9 0. 47 0. 31 Recycle Gas Rate, CF/Bbl. feed. 2, 580 2, 975 2, 778 Percent H2 71 71 71 Reaction Period, Hours 10 4 Product Dtstrlbution: 04/430 FV'I, Vol. Percent 17.1) 04, Vol. Percent 5. 8 05/430 FVT, Vol. Percent. 71. 7 05, Vol. Percent 4. 6 (J /430 PVT, Vol. Percent. 67. l Cfl/2l5 FVI l0. 7 215/430 FV'I. .10. -l Polymer, 430 PVT. l. 1 Dry Gas, Wt. Percen l2. 1 Carbon, Wt. Percent. 1. 2 Inspections O5I43O FVT:

Research Oct. No. C1 915. d Volatility (D only) Percent ofi at- Olefius, v01. percent on F1! 0. 0 2. 1 4. 2 Aromatics 7. 1 21.0 l 37. 5 Namhenes. 21. 2 6. 4 ..l 2. 8 Puraflins 71.7 58.0 a 22.0 Total 1 0 s7. 5 1 67.1

The foregoing description contains a limited number of embodiments of the present invention. It will be understood, however, that numerous variations are possible without departing from the scope of the following claims.

What is claimed is:

l. A process for upgrading hydrocarbon materials which comprises contacting a naphtha-kerosene fraction with a molybdenum oxide-containing reforming catalyst in a first reaction stage in the presence of hydrogen-containing gas at pressures of 200-1000 lbs. per sq. in. and at temperatures of 850 to 950 F. to convert substantially all of the naphthenic constituents to aromatics, expanding the eflluents from this reaction stage to a lower pressure to flash overhead hydrogen-containing gas and naphtha boiling up to 400 F. from a bottoms fraction comprising heavy naphtha/ kerosene, subjecting the overhead gaseous stream to contact with a molybdenum oxidecontaining reforming catalyst in a second reaction stage at pressures from atmospheric to lbs. per sq. in. and at temperatures of from 925 to 1000 F. to convert a substantial portion of the paratfinic constituents to aromatics,

2. The process as defined in claim 1 wherein the catalyst employed in both stages consists of 10 to 12 wt. per cent M003 on activated alumina.

3. The process as defined in claim 1 wherein the catalyst employed in both stages consists of 10 to 12 wt. per 5 cent M003 on zinc aluminate spinel.

References Cited in the file of this patent UNITED STATES PATENTS 2,285,727 Komarewsky June 9, 1942 6 Linn et al. July 31, 1945 Oblad Aug. 21, 1945 Layng et a1. Jan. 1, 1946 Schulze Apr. 16, 1946 Levine et al June 21, 1949 Black June 28, 1949 

1. A PROCESS FOR UPGRADING HYDROCARBON MATERIALS WHICH COMPRISES CONTACTING A NAPHTHA-KEROSENE FRACTION WITH A MOLYBDENUM OXIDE-CONTAINING REFORMNG CATALYST IN A FIRST REACTION STAGE IN THE PRESENCE OF HYDROGEN-CONTAINING GAS AT PRESSURES OF 200-1000 LBS. PER SQ. IN AND AT TEMPERATURES OF 850 TO 950* F. TO CONVERT SUBSTANTIALLY ALL OF THE NAPHTHENIC CONSTITUENTS TO AROMATICS, EXPANDING THE EFFUENTS FROM THIS REACTION STAGE TO A LOWER PRESURE TO FLASH OVERHEAD HYDROGEN-CONTAINING GAS AND NAPH- 